Method and apparatus for utilizing energy from radioactive material



AL 1 2,765,414 UTILIZING MATERIAL 1956 s. L. GENDLER ET METHOD AND APPARATUS FOR ENERGY FROM RADIOACTIVE Flled Nov 7 1950 2 Sheets-Sheet 1 STANLEY 1.. GENDLER 3 HARRY A. KOCH,

IN VEN TORS- A 7'TOR/VEK Oct. 2, 156 s GENDLER ET AL 2,765,414

METHOD AND APPARATUS FOR UTILIZING ENERGY FROM RADIOACTIVE MATERIAL Filed NOV. 7, 1950 2 Sheets-Sheet 2 STANLEY L. GENDLE'R8 HARRY A. KOCH,

INVENTORS.

A Tram/Ex United States Patent 2,765,414 Patented Oct. 2, 1956 METHOD; AND APPARATUS FOR; UTILIZING ENERGY FROM. RADIOACTIVE MATERIAL Stanley Eawrence Gendler, Los Angeles, and Harry A.

Koch; Venice, Califi, assignors to- The Rand Corporation,:SahmMonica, Calif;

Application November 7,.1950,.Serial:No. 194,514

IT Glhilils; (Gll- 290- 2) This inventionrelates to adevice and method for convertin'g"-' energy from radioactive material to electrical energy and more particularly for obtaining from radioactive material a regulated; as for example a constant electrical power supply, and still more particularly an electrical power supply at regulated or constant voltage.

As isgenerally known, power supplied byradioactive mate'rial' is not constant with time but drops off in accordance with a characteristic activity decay curve. Accordingly,- when radioactive material is used as a source of power, the power available is first relatively large and then falls oif'with'tirne in accordance with the particular characteristicdecay curve for the particular material used. For many applications involving the use of radioactive material as a source of power, it is' desirable to control the amount of power available as for example at a constant value. When converting to a supply of electrical energy,- it isdesiralile to obtain an electrical power supply at regulated voltage, which for most applications will be at a regulated constantvalue. Also, for some purposes it is desirable to do this with" as little equipment as possible, particularly with as little weight as possible. This is-espeoially true for providing-an auxiliary power supply for operating controls and various auxiliary devices of a rocket whereboth space and weight must be kept low.

In accordance-with this invention power from radioactive material is converted toelectrical'pow'er' at' a value less-than the initial power available from the radioactive material and the excess of' power from the radioactive material is dissipated in a manner to maintain the con verted electrical power at a regulated value, for example, substantially constant; or more particularly at a regulated voltage which preferably is a regulated constant voltage. This is accomplished by dissipating a sufficient amount, that is, the excess of the'energy fromthe radioactive material to maintain the converted electrical power at the desired regulated value;

In accordance with one embodiment ofmy'invention in a nuclear reaction power source, a quantity of radioactive material is enclosed within a sphere a portion of which is opaque to outward radiation from the sphere and another portion is transparent to or will permit outward radiation of energy and this transparent portion has an adjustable opaque or reflecting cover to adjust the amount of radiation dissipated" through the transp arentportion by increasin or decreasing its area by moving tue'opaque cover over a greater or lesser area of the transparent portion. Thissource of power from radioactivematerial so controlled is converted to" electrical power preferably by means of a mercury vapor system the heatirig tube for which is placed within the radioactive material and the mercury vapor system used for converting power into electrical power preferably by means-0f a mercuryvapor engine driving an electrical generator. To maintain the supply of electrical power" at a controlled or regulated value, the. extent to which the opaquecover; extends over the. transparent. areaof thesphereiscont-rolledinaccordance'with the electrical power output. For.examp1e, to maintain a controlled electrical power output, the opaque cover position may be adjusted in accordance with the voltage produced by the electrical generator in such a manner that When the'voltage goes above a given value the opa'que cover is moved to expose more transparent area and when the voltage goes below a given value the opaque cover is moved to cover more of the transparent area to respectively increase or decrease the energy dissipated and to respectively decrease or increase the radioactive power converted to electrical power so that it is thereby adjusted and controlled to the desired constant value of voltage.

My invention will be further illustrated and described in connection with the accompanying drawing in Which Figure l is a perspective view of the radioactive heating unit showing a portion of the sphericalcontainer or boiler cut away.

Figure 2 is a detailed view on the line 22 of Figure 1 showing the mechanical arrangement for moving the opaque cover, with the cover in fully closed position.

Figure 3 is a detailed view on the line 33 of Figure 1 showing how the spherical container and adjustable cover are supported.

Figure 4 shows schematically the arrangement for using the radioactive heating device for converting the radioactive. power to electrical. power and controlling the conversion to maintain a regulated electrical power output.

Referring now particularly to Figure 1, at 1 is shown a spherical container or boiler the interior 2 of which is substantially filled with'radioactive material. The radioactive material is omitted from the drawing for a clearer showing of the interior structure and arrangement of the radioactive heating unit inside the spherical. container. The radioactive material is a molten liquid which may be put into or removed fromthe spherical container through opening 3 having removable plug 4. The spherical container l is preferably made of beryllium. Beryllium has a surprising combination of properties making it readily suitable for this purpose, particularly including low density, high melting point, it produces very little secondary gamma-radiation (Brernsstrahlu-ng), has high conductivity for conducting excess heat to its outer surface, and provides a surface with a high emissivity. The thickness of the spherical container 1 should be greater than the maximum range of 3 m. e. v. beta particles in beryllium, which is about 8.5 millimeters to shield against beta-radiation. inside the spherical container 1 is a paddle 5, also preferably made of beryllium, mounted on a rotatable shaft 6 which is preferably hollow and preferably made of ceramic such as carborundum. The paddle 5 is provided to stir the molten liquid containing the radioactive materialto avoid development of hot spots in the molten liquid. Also, inside the spherical container within the molten radioactive material is a boiler tube 7 also preferably made of beryllium. This tube conducts the working fluid, preferably mercury vapor, through the molten radioactive material.

Extending over the lower hemisphere of the. spherical container 1' is an opaque reflecting cover or' shell 8 preferably of steel gold plated on both sides with an air gap 9 between the shell 8 and sphere 1 to reduce heat loss. by conduction. This gold plated steel shell8 provides a fixed cover over the lower hemisphere of the sphere 1 and reflects thermal radiation back to the interior of the sphere. This gold plated steelshell maintains a high infra-red refiectivitity and low emissivity even at high temperature.

The upper hemisphere lllof sphere l hasnofixed cover and when uncovered serves as' a radiator. to radiate- 'tliermal energy into space from the beryllium surface. The area of this radiation surface and the extent of such radiation of energy into space is adapted to be varied by adjustable cover 11. This adjustable cover 11 is also a gold plated steel shell the same as the fixed cover 8. Adjustable cover 11 is mounted to rotate about an axis as represented by shaft 6 from an extreme open position in which the entire upper hemisphere 10 is uncovered to the other extreme position in which the entire upper hemisphere 10 is covered. Adjustable cover 11 is in the shape of a hemisphere and is adapted to fit over the clear fixed cover 8 so that when drawn over hemisphere 10 an air space 12 is left between the surface of hemisphere 10 and the adjustable cover 11 to reduce heat loss by conduction. Slots 7a are provided in cover 11 as shown to fit over tubes 7 when cover 11 is in a fully closed position.

The variation of the position of adjustable cover 11 is preferably mechanically accomplished by means of a motor 13 connected by shaft 14- to pinion 15 which meshes with rack 16 on the periphery of adjustable cover 11. The gear teeth of rack 16 extend a short distance, as at 16', beyond the edge of the adjustable cover 11 so that by means of pinion 15 the adjustable cover 11 may be readily moved to a completely closed position as particularly illustrated in Figure 2.

The whole radioactive heating unit including the sphere 1, fixed cover 8, adjustable cover 11 and hollow shaft 6 are conveniently supported on a bracket member shown generally at 17 having two upright supporting members 18 and 19 the upper portions of which are each provided with bearings for supporting the shaft 6 and sphere 1, fixed cover 8 and adjustable cover 11. The detail of the supporting arrangement is shown particularly in Figure 3. Hollow shaft 6 is fitted into a ceramic bearing 20, preferably carborundum. On bearing 20, sphere 1 and fixed cover 8 are fixed. Extending as part of fixed cover 8 is a protruding bearing member 21 which extends over bearing member and to which the upper portion of upright member 18 is fixed by set screw 22. Adjustable cover 11 is arranged to rotate about bearing member 21. For this purpose there is provided an anti-friction annular hearing member 23 between 21 and adjustable cover 11. The outer end of shaft 6 is connected to motor 28 for turning paddle 5.

The preferred radioactive material to be filled into spherical container 1 is cerium 144. It is available as a by-product of a pile, and has a half-life of about 275 days. It emits mainly high-energy beta-rays, which are the least dangerous. This radioactive material is preferably diluted at a ratio of 100 diluent to 1 part by weight of cerium 144 with stable nonradioactive cerium 140. This avoids any chemical reaction effects due to heat or radiation because of the use of a single chemical species. This radioactive material emits high energy particles which when slowed down in passing through the cerium 140 diluent produces heat which in turn is supplied to the mercury vapor or other working fluid in tube 7. Thus it will be seen that the cerium 140 serves not only to convert radioactive energy into heat but serves as well as part of a heat exchanger body to transfer the heat energy to the mercury.

As pointed out above, the radioactive power from the radioactive material is converted into electrical power preferably by means of a mercury vapor system. This is more particularly shown in Figure 4 where at 26 is shown schematically a compound piston engine operated by mercury vapor. The mercury is heated and vaporized in tube 7 immersed in the radioactive material within spherical container 1 and the heated mercury vapor is passed to the engine 26 through tube 27. The mercury vapor expands in engine 26 and is exhausted to a radiant condenser 28 and mercury is pumped therefrom by pump 29 back to heating tube 7. The engine 26 is used to drive electrical generator 30 and through leads 31 connects to voltage regulator 32 which in accordance with any desired voltage setting operates as a feedback control to run motor 13 in a direction tocl'ose adjustable cover 11 if the voltage drops below the given value, or to open adjustable cover 11 if the voltage goes above the given value. Also, from leads 31 there may he leads 33, connecting motor 28 and leads 34 for connecting motor 35 which drives pump 29.

In order to prevent the radioactive heating unit from overheating to a dangerous temperature a temperature sensitive element, not shown on the drawing) such as a thermocouple may be placed in the spherical container 1 and connected to override the voltage regulator 32 to open adjustable cover 11.

Also, instead of controlling the position of cover 11 by the electrical output voltage, the control may be, in accordance with a modification of my invention, effected by a thermostat having its thermosensitive element within the spherical container 1 electrically connected to a controller (not shown on the drawing) to cause motor 13 to open cover 11 when the temperature in sphere 1 goes above a set value and to close cover 11 when the temperature falls below a set value.

In operation the voltage regulator 32 will be set at the value of voltage which is desired to maintain on the electrical system. With the conversion system in operation, if the voltage at 32 is too high regulator 32 will cause motor 1.3 to operate in such a direction that adjustable cover 11 will be moved to expose more of radiation surface 10 to allow dissipation of radioactive energy by radiation from surface 10 and to decrease the amount of heat imparted to the mercury vapor in tube 7. This will slow down the electrical generator until the voltage drops to the desired value. If, on the other hand, the voltage at 32 is too low, regulator 32 will cause motor 13 to operate in the opposite direction to cause a closing of adjustable cover 11 to reduce the exposed portion of radiation surface 10 and thus retain more heat in boiler 1 and increase the heat supply to the mercury vapor in tube 7. In this manner it will be seen that the energy output from the electrical system can be thus regulated in terms of the voltage. Moreover, since the regulation as here shown is in accordance with the voltage, the electrical power supplied to the power system will be that amount of power required to maintain a constant voltage. It will be understood of course that in any event the regulation here described and contemplated is within the upper and lower limits of the device. Furthermore, in accordance with this arrangement the automatic control will maintain a constant voltage for the electrical power output even though due to the activity decay the power from the radioactive material drops off with time. As the activity of the radioactive material declines with time and the voltage drops below the set value, the cover 11 will automatically be closed to retain sufficient heat in the spherical container or boiler 11 to cause the mercury vapor system to deliver enough power to the generator to maintain the required voltage. This will take place until the cover 11 has been adjusted to it's completely closed position.

Although in accordance with my invention harmful radiations have been materially reduced, it will be understood, of course, that in order to eliminate any risk, per sonnel should be properly shielded especially within the proximity of such a unit, in accordance with known procedures.

The above description and specific embodiments are intended to illustrate my inventionv and not to limit the scope thereof, and my invention extends to all modifications and variations which fall within the scope of the appended claims.

We claim:

l. In a device for converting energy of radio-active material into a form of energy appearing as an increase in temperature of mercury vapor of a mercury vapor system, the combination comp-rising a container having walls of beryllium containing cerium 144 as the radio-active material and relatively a substantially large proportion of cerium 140 as a diluent therefor and as an absorber of radio-active energy therefrom, at least a portion of the beryllium walls of said container covered by an opaque reflecting steel cover plated on both sides with gold with space between the beryllium wall and said cover, and a beryllium tube extending through said wall of beryllium and forming a heat exchange coil within the mixture of cerium 144 and cerium 140 within said container so that heat absorbed by said cerium 140 is transferred to said beryllium tube and to mercury vapor therewithin.

2. In a device as defined in claim 1 having means for varying the portion of said veryllium walls covered by said opaque reflecting cover.

3. The device as defined in claim 2 in which said por tion is varied in accordance with a measure of the energy converted.

4. The method of regulating the rate of usable heat energy delivered by a nuclear reaction power source, which comprises the steps of: absorbing in a heat exchanger body, the radioactive emanations from a radioactive body to convert said emanations into heat; conducting a portion of said heat from said heat exchanger body to a heat engine to utilize said portion and radiating the remaining portion of heat from said heat exchanger body; and reflecting a progressively increasing portion of said radiated heat back to said heat exchanger body whereby to compensate for th decreasing heating of said heat exchanger body due to the decay in rate of emana tions from said radioactive body, thereby to produce a substantially uniform rate of delivery of heat to said heat engine.

5. The method of regulating the rate of usable heat energy delivered by a nuclear reaction power source which comprises the steps of: absorbing in a heat exchanger body the radioactive emanations from a radioactive body to convert said emanations into heat; conducting a portion of said heat from said heat exchanger body to a heat engine to power the latter; radiating from said heat exchanger body the heat which is not delivered to said heat engine; employing said heat engine as a prime mover to generate electric power; reflecting a variable portion of said radiated heat back to said heat exchanger body whereby to augment the heating thereof; and increasing the portion of heat reflected to said heat exchanger body in inverse proportion to the voltage of said electric power, whereby to maintain a substantially constant rate of delivery of heat to said heat engine.

6. A nuclear reaction power source comprising: a body of radioactive material; a heat exchanger body adjacent said radioactive material and arranged to absorb substantially all of the radioactive emanations therefrom whereby to heat said heat exchanger body; power conversion means positioned in heat transfer relation to said heat exchanger body whereby to convert a first portion of thermal power from said heat exchanger body to another form of power; means surrounding said heat exchanger body to dissipate a second portion of the thermal power from said heat exchanger body; and means operatively associated with said dissipating means to progressively reduce said second portion of power dissipated thereby whereby to compensate for loss of heating due to decay of said radioactive material.

7. A nuclear reaction power source comprising: a body of radioactive material; a heat exchanger body adjacent said radioactive material and arranged to absorb substantially all of the radioactive emanations therefrom whereby to heat said heat exchanger body; power conversion means positioned in heat transfer relation to said heat exchanger body whereby to convert thermal power from said heat exchanger body to another form of power; means surrounding said heat exchanger body to dissipate a portion of the heat from said heat exchanger body; means operatively associated with said dissipating means to vary the portion of heat dissipated thereby; and feedback means coupled between said conversion means and said varying means to adjust the latter in response to the power level of the output of said conversion means where by to maintain said power level substantially constant over a given period of time during which there is a substantial reduction in radioactive emanations from said radioactive material.

8. A nuclear reaction power source comprising: a body of radioactive material; a heat exchanger body adjacent said radioactive material and arranged to absorb substantially all of the radioactive emanations therefrom whereby to heat said heat exchanger body; heat engine means positioned in heat transfer relation to said heat exchanger body whereby to convert heat in said heat exchanger body to another form of power; means forming a radiator in heat transfer contact with an outer surface of said heat exchanger body to absorb and radiate therefrom, heat in excess of that converted as aforesaid; and an adjustable reflector in the path of heat radiated from heat exchanger body, and arranged to return a variable portion of said radiated heat to heat exchanger body whereby to vary the amount of heat lost by radiation from said heat exchanger body to compensate for loss of thermal power due to decay of said radioactive material.

9. The construction of claim 8 further characterized by having feedback means coupled between said heat engine means and said reflector to adjust the latter in response to the power level of the output of said heat engine means whereby to maintain said power level substantially constant.

10. A nuclear reaction power source comprising: a radioactive body comprised of cerium 144 diluted with cerium a beryllium container completely surrounding said radioactive body, and of sufflcient thickness to absorb substantially all of the radioactive emanations from said body and convert the same into heat, said container being in heat transfer contact with said body to heat the same and having a heat radiating exterior surface; a boiler in heat transfer contact with said body; shell means partially surrounding said container and having an inner reflecting surface adapted to returned to said container, a substantial portion of the heat radiated therefrom; and means to adjust said reflector to vary the amount of heat returned as aforesaid whereby to compensate for loss of heating due to decay of said radioactive body.

11. The construction of claim 10 further characterized by having control means responsive to the power level in said boiler and connected to said adjusting means whereby to maintain said power level substantially constant over a given period of time.

References Cited in the file of this patent UNITED STATES PATENTS Re. 19,114 Stein et a1 Mar. 13, 1934 1,192,775 Emmet July 25, 1916 1,743,621 Quinn i. Jan. 14, 1930 1,753,287 Fai'lla Apr. 8, 1930 2,053,061 Bristol Sept. 1, 1936 2,433,725 Ziebolz Dec. 30, 1947 2,452,581 Lehmann Nov. 2, 1948 2,517,120 Linder Aug. 1, 1950 2,579,311 Fairey Dec. 18, 1951 2,592,115 Carroll Apr. 8, 1952 FOREIGN PATENTS 129,873 Great Britain July 24, 1919 233,011 Switzerland Oct. 2, 1944 OTHER REFERENCES Abstract of abandoned application Serial No. 526,338, E. G. Segre, filed March 13, 1944, published November 29, 1949, class 250-65, 250106. 

1. IN A DEVICE FOR CONVERTING ENERGY OF RADIO-ACTIVE MATERIAL INTO A FORM OF ENERGY APPEARING AS AN INCREASE IN TEMPERATURE OF MERCURY VAPOR OF A MERCURY VAPOR SYSTEM, THE COMBINATION COMPRISING A CONTAINER HAVING WALLS OF BERYLLIUM CONTAINING CERIUM 144 AS THE RADIO-ACTIVE MATERIAL AND RELATIVELY A SUBSTANTIALLY LARGE PROPORTION OF CERIUM 140 AS A DILUENT THEREFOR AND AS AN ABSORBER OF RADIO-ACTIVE ENERGY THEREFROM, AT LEAST A PORTION OF THE 